Archaeological Journal/Volume 2/Notices of New Publications: The History of the Art of Warming and Ventilating Rooms and Buildings
This is an interesting work, apparently written with much care and research. The author undertakes to illustrate the theories of warmth and cold, and begins ab ovo by an account, not unentertaining, of the climate, dress, and comparative comforts of many different nations: he shews the effects on the individuals of each nation resulting from the greater or less degree of heat they enjoy by the aid of natural or artificial means, and points out many important moral and physical peculiarities which, he says, not untruly, may be referred to the same cause; he then discusses at length the state of the ancient world in this matter, and draws a picture, sufficiently cheerless and uncomfortable, of the manners of the Egyptians, Jews, and Greeks.
But the portion of his labours most valuable to the archæologist, will be found in his third Essay, in which he enters with considerable minuteness into the construction of the Roman hypocaust. As the subject is one not wholly uninteresting to the inhabitants of an island in which Roman remains are found in profusion, and as such details are not generally accessible, we propose to give the sum of what he states upon the subject of the hypocaust.
The objects of the hypocaust were two-fold, either to supply heat to the water with which warm baths were filled, or to heat the caldarium, or dry sweating room. Our author describes its construction for the second purpose thus; "The floor is made inclining, so that a ball placed on any part of it would roll towards the fire-place, by which means the heat is more equally diffused in the sweating chamber. The floor is paved with tiles eighteen inches square; and on these are built brick pillars, eight inches on the side and two feet high, and cemented with clay and hair mixed together. The pillars are placed at such a distance as will allow tiles two feet square to be laid on them to form the ceiling of the hypocaust and support the pavement of the caldarium. The air to the caldarium, or room over the hypocaust, is admitted through an aperture in the centre of the roof, from which a brazen shield is suspended by chains. By raising or lowering this shield, which opens or shuts the aperture, the heat of the caldarium is regulated[1]."
Secondly. "For heating the water to supply the baths, there are to be three caldrons, one for hot water, another for tepid, and a third for cold; arranged so that as the hot water runs out of the lower vessel, it may be replaced from the tepid vessel, and that in like manner replenished from the cold vessels[2]."
A third use of the hypocaust, viz. for heating domestic apartments, is stated by Seneca to have come into fashion within his memory. For this purpose, "The hypocaust being constructed in the under story of a building, and in the manner described by Vitruvius, several pipes of baked clay are then built into walls, having their lower ends left open to the hypocaust. These pipes were carried to the height of the first or second story, and had their upper orifices made to open into the chamber that was to be heated. They were closed by moveable covers."
It is clear that this system must have been subject to many of the evils attendant on the use of the simple charcoal brazier, and it appears from Seneca that they were considered as unwholesome, as similar methods of heating are now found to be.
The author then enters more fully into the details of the construction of the heating apparatus, and gives several woodcuts which illustrate admirably his statement of the case. The first of these illustrations enables us to present to our readers the representation of the caldarium resting on its pillars. [3]footnote of unknown location (Wikisource contributor note)
The next woodcut gives a plan of the arrangement of the pillars, which rested upon a thick stratum of cement, composed of lime and pounded bricks. The floor of the caldarium itself was made of a stratum of cement nine inches thick, ornamented by mosaics. The sides were hollow, so as to permit the warm air from the hypocaust to ascend to the cornice of the room. 
The contrivance whereby this was effected is curious, and is clearly shewn in the figures here given, in the former of which we see the flat surface of the tiles which lined the Thermal chamber, with their fastenings at each corner; in the latter, a vertical section of the same chamber, shewing the manner in which the tiles were attached to the wall.
Adjoining to the caldarium was the tepidarium, which, as its name implies, admitted the use of only a moderate temperature, a flue passed under it connected with those of the caldarium and hypocaust, but its real warmth proceeded from a large brazier of bronze lined with iron, at one end of it[4], in which the boilers were placed, as exhibited in the figure here given. It has, however, been conjectured that in the great baths at Rome some better system for heating must have been adopted. The supply of water was conveyed by an aqueduct into a cistern placed above them, and open to the air, so that it might be warmed as much as possible by the sun, before it was admitted to the boilers.
In some cases, the water was heated by earthenware pipes, which passed through them full of hot air from the hypocaust. Of this arrangement a more precise notion may be obtained from the woodcut in the following page.
Many practical difficulties co-exist with such a system of heating, and in the cases of the largest Thermæ the radiation was probably so great as to prevent any great heat being conveyed to the chamber. Cameron (Baths o the Romans) has entered into a long calculation to shew that the plan was feasible, but after all, it was more likely that the hypocausts in these baths were used to preserve the temperature which had been given to the water by some other means not now known to us.
Our author then describes Pliny's Laurentine villa, which, as he shews, was constructed with hypocausts such as have been already noticed, and then proceeds to remark at considerable length upon the remains of Roman villas in England. In these the hypocausts seem to have been chiefly of two kinds, those which were constructed with flues running under the floor of an apartment, and heated from a fire-place external to the building; or else constructed like a low chamber, with a ceiling supported (as Vitruvius directs) by small pillars, or dwarf walls, and occasionally having flues leading from them under other apartments.
A detailed description is then given of the construction of Hadrian's villa at Woodchester, which is the most magnificent discovered in Britain, but it does not materially differ from the preceding[5]. In two instances only have means for the use of open fires (in some degree like our own) been discovered. There were two rooms in the Roman villa at Bignor, in Sussex, with hearths against the wall, enclosed by jambs like a modern fire-place. In the villa likewise discovered in 1823, at Bramdean, Hampshire, remains of an open fire-place without vault or flues were discovered[6]. This last example had not been noticed by Mr. Bernan.
No chimneys have been discovered; but this may be accounted for from the falling in of the upper part of the walls; although the arguments seem strong against their early use in Italy, it is probable that with this arrangement of their fires, the Romans had also the use of chimneys.
The whole of the work seems to be arranged skilfully and drawn up with care; it comprises much information valuable to the student of antiquities, and will well repay the perusal of those who are interested in the theories and practice of warming and ventilating houses.
- ↑ See also engravings to article "Baths," in Dict. of Greek and Roman Antiquities, pp. 136, 142, (edited by William Smith, Ph.D., London, 1842,) in which this arrangement is very distinctly shewn.
- ↑ See engraving, Dict. of Antiq., p. 145.
- ↑ See Winckelman, Lett. on Herculaneum.
- ↑ See engraving, Dict. of Antiq., p. 139.
- ↑ The reader may compare the engravings of the hypocaust, &c., recently discovered at Wheatley, described in the present number, pp. 350, &c.
- ↑ Sketches of Hampshire, by John Duthy, p. 40; where a detailed account of this villa, and plates of two fine tesselated pavements, are given.